Transversely stretched nonwoven fabric with high tensile strength stretched seven times wider or more in transverse direction

ABSTRACT

A transversely stretched nonwoven fabric is manufactured by transversely stretching a nonwoven fabric. First, an original web comprising a plurality of un-oriented filaments is heated to a temperature higher than its stretch suitable temperature by 5° C. or more. Next, the heated original web is stretched at a rate of 1.2 to 3 in its transverse direction to stretch the filaments of the original web with almost no molecular orientation involved. Then, the original web stretched transversely at a rate of 1.2 to 3 is heated to the stretch suitable temperature and the original web is further stretched transversely at the stretch suitable temperature. With these steps, a transversely stretched nonwoven fabric in which the original web is stretched transversely at a rate of 7 times or more in total as compared with the state of the stretch thereof is manufactured with a high tensile strength of 132.5 mN/tex (1.5 g/d) in the transverse direction.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a transversely stretchednonwoven fabric of large width manufactured with transverse stretch ofstretching a web in its transverse direction as one of so-called poststretch methods for nonwoven fabrics in which a web formed from spunfilaments is stretched in manufacturing a nonwoven fabric. Thetransversely stretched nonwoven fabric is used as a nonwoven fabricrequiring strength in a transverse direction and as a material web foran orthogonal nonwoven fabric, or as a nonwoven fabric with strength anddimensional stability.

[0003] 2. Description of the Related Art

[0004] Methods of manufacturing nonwoven fabrics include a spun-bondingscheme, a melt blow scheme, a spun lace scheme which form a nonwovenfabric directly from spinning of a melting material resin, and the like.These schemes are dominant in the nonwoven fabric manufacturing methodsin terms of economics and manufacturablility. Nonwoven fabricsmanufactured with these schemes are hereinafter referred to as spunbonded nonwoven fabrics in a broad sense. The spun bonded nonwovenfabrics in a broad sense with the prior art are random nonwoven fabricswhich have disadvantages that strength is low and they often have nodimensional stability.

[0005] Methods and apparatuses for manufacturing nonwoven fabrics whichimprove the aforementioned disadvantages are described in JapanesePatent Publication No. 36948/91, Japanese Patent Publication No. 6126/95and Japanese Patent No. 2612203 by the present applicant.

[0006] Japanese Patent Publication No. 36948/91 describes, as a methodof manufacturing a nonwoven fabric, a method of stretching a long fibernonwoven fabric formed by spinning un-oriented filaments in onedirection at a stretch suitable temperature such that many of thefilaments are aligned in one direction. The gazette describes a methodof laminating and bonding nonwoven fabrics stretched in such a methodsuch that the respective stretch directions of the nonwoven fabrics areorthogonal to each other.

[0007] In addition, the aforementioned-gazette describes, as sprayspinning, a method of manufacturing a long fiber nonwoven fabriccomprising un-oriented filaments aligned in one direction. In the methodof manufacturing a long fiber nonwoven fabric, first, filaments pushedout from a nozzle are scattered by heated air which rotates in a spiralover a screen mesh running in one direction. Besides the rotating air,two flows of air are jetted such that they collide with each other belowthe nozzle. The air spread by the colliding two flows of air furtherscatters the rotating spun filaments. When the directions of the twoflows of air jetted such that they collide with each other are parallelto the running direction of the screen mesh, the spun filaments arescattered in a direction perpendicular to the running direction of thescreen mesh. This causes the scattered filaments to be accumulated onthe screen mesh with many of the components being aligned transversely,thereby manufacturing a nonwoven fabric with the filaments mainlyaligned transversely. On the other hand, when the directions of the twoflows of air jetted such that they collide with each other aresubstantially orthogonal to the running direction of the screen mesh,the spun filaments are scattered in a direction parallel to the runningdirection of the screen mesh. This causes the scattered filaments to beaccumulated on the screen mesh with many of the components being alignedlongitudinally, thereby manufacturing a nonwoven fabric with thefilaments mainly aligned longitudinally.

[0008] Japanese Patent Publication No. 6126/95 describes, as sprayspinning, a method of manufacturing a nonwoven fabric with one directionalignment in which a plurality of filaments are aligned substantially inone direction. In the manufacturing method, when filaments are spun bydischarging polymeric materials from a port for spinning, first, thespun filaments are rotated or vibrated in a width direction. While therotating or vibrating filaments have draft properties by a factor of twoor more, the filaments are acted on by a pair of fluids or moresubstantially symmetrically about one of the rotating or vibratingfilaments from the side of the filament. “Draft properties” refers tothe property of how much filaments are drawn. Such action of the pair offluids or more on the filaments causes the filaments to be scattered ina direction perpendicular to the discharged direction of the filamentswhile draft is applied to the filaments. As a result, the filamentsaligned in the scattered direction thereof are laminated in layered formto manufacture a nonwoven fabric with one direction alignment comprisingthe laminated filaments. “Draft is applied to the filaments” refers todrawing and thinning of the filaments by applying traction to them.

[0009] Japanese Patent No. 2612203 describes, as a method ofmanufacturing a nonwoven fabric, a method of manufacturing a web made offibers aligned in one direction. In the manufacturing method, fibers arejetted together with a fluid from an ejector onto a running beltconveyor, and the fibers are collected on the belt conveyor such thatthe fibers are aligned in one direction. In an example of such amanufacturing method, at least part of the conveyor belt is curvedperpendicularly to its running direction and downward such that thefluid and the fibers are jetted from the ejector toward the bottom ofthe curved portion in groove shape in the conveyor belt. The jettedfluid is scattered in a longitudinal direction of the groove in theconveyor belt, thereby aligning the fibers in the scattered direction.

[0010] In manufacturing the nonwoven fabrics, manufacture of a web oflarge width with high strength of a nonwoven fabric maintained is animportant factor since not only does it mean an increase in productionefficiency and a reduction in manufacturing unit cost, but also in termsof applications of the web, some fields find no applicability unless aweb of large width is used.

[0011] Since a transversely stretched web is manufactured by stretchingan original web in its transverse direction, it is easily obtained as aweb of large width in general. In the spray spinning described in theaforementioned Japanese Patent Publication No. 36948/91 and JapanesePatent Publication No. 6126/95, since an original web before stretchtypically has a width of 300 to 400 mm, the transverse stretch rate ofthe web is 5 to 6 for a web made of polypropylene (hereinafter referredto as “PP”), or 5 to 6 for a web made of polyethylene terephthalate(hereinafter referred to as “PET”). Therefore, there is a problem of thedifficulty in realizing a transversely stretched nonwoven fabric with awidth of 2400 mm or more as a product. A web of large width with ahigher stretch rate can be manufactured by employing spinning conditionsfor increasing the diameter of filaments of an original web when theoriginal web is 1.5 manufactured with the spray spinning described inJapanese Patent Publication No. 36948/91 and Japanese Patent PublicationNo. 6126/95, and in this case more stable spinning is possible.

[0012] Conventionally, means for transversely stretching a web with bothedge portions thereof held is generally used as a transverse stretchapparatus for stretching a web in its transverse direction. In addition,as such a transverse stretch apparatus, a tenter frame for use instretching a film transversely can be used. Simple transverse stretchapparatuses are a pulley type transverse stretch apparatus, and for afilm, an example is described in GB Patent Specification No. 1213441. Anapplication of the apparatus to a nonwoven fabric is described inJapanese Patent Publication No. 3068/88, Japanese Patent Publication No.36948/91 (U.S. Pat. No. 4,992,124 Specification corresponding to thatgazette) which are the earlier inventions by the present inventors. Atransverse stretch apparatus with means composed by combining a pair ofupper and lower groove rolls has been used (Japanese Patent PublicationNo. 32307/84, U.S. Pat. No. 4,223,059 Specification).

[0013] In general, a transversely stretched web of large width can beobtained from an original web of small width by increasing a transversestretch rate. However, since stretch at a higher rate involves stretchbreaking of filaments at the stretch, the rate inevitably has alimitation. While it is possible to achieve only an increase in thestretch rate by increasing the temperature of an original web or thestretch temperature in stretching the original web, stretch at a hightemperature cannot ensure sufficient strength of the resultanttransversely stretched web in general. Thus, a stretch rate of the orderof 5 to 6 as described above can ensure a certain degree of strength,but at a stretch rate of 7 or more, it is difficult to manufacture atransversely stretched web of large width with a desired strength.

[0014] On the other hand, as a method of stretching a web in itslengthwise direction or a longitudinal direction there is a proximitystretch method. The proximity stretch is a method in which rollers areused for longitudinally stretching a web, for example, to perform alongitudinal stretch with an extremely reduced stretch distance for theweb. It is difficult to apply the proximity stretch which is applied tosuch longitudinal stretch to transverse stretch of a web. In thetransverse stretch, generally, an original web is transversely stretchedwith both edge portions thereof held. Therefore, it is desirable notonly to transversely align filaments constituting a web but also toextend each filament from one edge to the other edge in a widthdirection of the web in the transverse stretch of webs as compared withthe longitudinal stretch. Thus, the proximity stretch used in thelongitudinal stretch can not be applied to the transverse stretch, andthe transverse stretch methods and transverse stretch apparatuses in theprior art have a problem of the difficulty in realizing a high stretchrate with the high strength of a web being maintained.

[0015] In the transverse stretch, as a mechanism similar to theproximity stretch using rolls in the longitudinal stretch, JapanesePatent Publication No. 36948/91 describes a transverse stretch method ofgroove roll type, for example. The transverse stretch method of grooveroll type employs a pair of groove rolls which is arranged such thatpeaks of one groove roll match valleys of the other groove roll. Anonwoven fabric comprising un-oriented filaments is introduced betweenthe pair of groove rolls to transversely stretch the nonwoven fabric bymeans of the projections and depressions of the peaks and valleys of thegroove rolls. However, the transverse stretch method of groove roll typehas disadvantages of a low stretch rate, low uniformity of stretch andthe like, which render the method unsuitable as a stretch method forobtaining high strength of a nonwoven fabric. As a result, the methodcan be used for stretch of a nonwoven fabric which does not require highstrength, but it is not suitable for obtaining a high stretch rate andhigh strength.

[0016] In particular, the stretch of PET filaments has characteristicsof a narrow range of temperatures suitable for stretch at which highstrength of a nonwoven fabric is obtained, i.e., stretch suitabletemperatures at which high strength of a nonwoven fabric is obtained,and significant variations in the stretch suitable temperature dependingon a stretch speed and a stretch rate. These characteristics make itdifficult to stretch a web comprising PET filaments. Specifically, it isdifficult to obtain a transversely stretched web of large width withhigh strength maintained and at a high stretch rate as a web comprisingPET filaments. Therefore, stretch which can solve such difficulties mustbe performed in order to manufacture a web of large width comprising PETfilaments.

[0017] In such transverse stretch at a high rate, it is necessary notonly to achieve a high stretch rate, but also to provide uniformlystretched portions of a transversely stretched web obtained by stretchand to provide uniform strength distribution and basis weight in thestretched web, a reduced frequency of stretch breaking of filaments andthe like. Therefore, a method of transversely stretching a web at a highstretch rate does not provide stretch means in an industrial senseunless such uniform transverse stretch is realized.

[0018] When a transverse stretch apparatus used for the aforementionedpurposes is expensive or requires a large floor area, the transversestretch apparatus has no practicality as a nonwoven fabric manufacturingapparatus which has the requirement of being inexpensive. In addition,it is necessary for the transverse stretch apparatus to freely change astretch rate and to easily deal with troubles such as stretch breakingin a simple manner. Furthermore, even such a simple and inexpensivetransverse stretch apparatus must enable fast stretch and realizeuniform stretch at a high rate as described above. Particularly instretch of a nonwoven fabric, the aforementioned purposes such asstretch at a high rate, high-speed stretch, and uniform stretch cannotbe achieved unless an original material formed from collected flocculentfilaments and an apparatus are employed in the stretch, the apparatusbeing capable of completely replacing the air contained within thecollected flocculent filaments with a heated medium at a temperatureincreased to a stretch temperature.

SUMMARY OF THE INVENTION

[0019] It is an object of the present invention to provide atransversely stretched nonwoven fabric in which, when an original web istransversely stretched to manufacture a transversely stretched nonwovenfabric, high tensile strength can be obtained in the resultant nonwovenfabric in a transverse direction even at a stretch rate of the originalweb of 7 or higher, specifically, at least 132.5 mN/tex (1.5 g/d),desirably 158.9 mN/tex (1.8 g/d) or higher, more desirably 176.6 mN/tex(2.0 g/d) or higher, most desirably 220.8 mN/tex (2.5 g/d) or higher isobtained as a tensile strength of the web in the transverse direction, amethod of manufacturing such a transversely stretched nonwoven fabric,and a transverse stretch apparatus capable of manufacturing atransversely stretched nonwoven fabric at such a stretch rate andstrength.

[0020] It is another object of the present invention to provide atransversely stretched nonwoven fabric having texture like a cloth, amethod of manufacturing such a transversely stretched nonwoven fabric,and a transverse stretch apparatus capable of manufacturing such atransversely stretch nonwoven fabric. It is desired that the diameter offilaments constituting the stretched web is at least 20μm or lower,desirably 10 μm, more desirably 5 to 8 μm.

[0021] It is a further object of the present invention to provide atransverse stretch apparatus which, when an original web is heated inorder to transversely stretch the original web to manufacture atransversely stretched nonwoven fabric, allows quick and uniform heatingof the original web to provide fast and uniform stretch of the originalweb at a high rate, and a heating unit for use in the transverse stretchapparatus.

[0022] To achieve the aforementioned objects, the transversely stretchednonwoven fabric according to the present invention comprises a pluralityof transversely aligned filaments with a fiber diameter of 20 μm orlower, has a stretch rate of 7 or more in a transverse direction, andhas a tensile strength of 132.5 mN/tex (1.5 g/d) or higher in thetransverse direction. For the tensile strength of a transverselystretched nonwoven fabric, breaking strength is represented as abreaking load per 5 centimeters in the long fiber filament nonwovenfabric test method in compliance with JIS (Japanese IndustrialStandards) L1906. However, the present invention employs representationof tensile strength as strength per tex (mN/tex) with conversion fromthe weight of a nonwoven fabric to fineness (tex) since nonwoven fabricsof various basis weights have been tested. For reference, strength perdenier (d) is also shown in the following description. The realizationof the aforementioned transversely stretched nonwoven fabric can resultin a web of large width at a stretch rate of 7 or more in the transversedirection while a high tensile strength of 132.5 mN/tex (1.5 g/d) orhigher is maintained. This causes enhanced production efficiency of thetransversely stretched nonwoven fabric and reduced manufacturing unitcost of the transversely stretched nonwoven fabric as a web of largewidth. In addition, such a transversely stretched nonwoven fabric withhigh strength and a high transverse stretch rate obtained as a web oflarge width leads to wide applicability of the transversely stretchednonwoven fabric in terms of applications of the web. Moreover, since thefiber diameter of the filaments constituting the transversely stretchednonwoven fabric is 20 μm or lower, the transversely stretched nonwovenfabric has the texture of cloth.

[0023] In the method of manufacturing the transversely stretchednonwoven fabric according to the present invention, first, an originalweb comprising un-oriented filaments is stretched 1.2 to 3 times widerin its transverse direction at a temperature higher than its stretchsuitable temperature by 5° C. or more. This step causes the filaments ofthe original web to be stretched with almost no molecular orientation ofthe filaments involved. At this point, the strength of the original webis not increased yet. If the stretch rate in the transverse direction is1.2 or lower at this step, the original web cannot be transverselystretched at a high rate at the next step, and if the stretch rate is 3or higher, the strength of the original web is reduced. Next, theoriginal web stretched 1.2 to 3 times wider in the transverse directionis further stretched transversely at the stretch suitable temperature tostretch the original web 7 times wider or more in the transversedirection in total as compared with the state of the original web beforethe stretch. In this manner, a transversely stretched nonwoven fabricmade of the original web stretched 7 times wider or more in thetransverse direction in total is manufactured. At this step, theoriginal web is transversely stretched at a high rate at the stretchsuitable temperature of the original web, and it is possible to obtain atensile strength of the transversely stretched nonwoven fabric in thetransverse direction equal to or higher than that in normal stretch atthe stretch suitable temperature. The method of manufacturing thetransversely stretched nonwoven fabric including the two-step stretchprovides a web of large width stretched at a high rate of 7 or morewhile a high tensile strength of 132.5 mN/tex (1.5 g/d) or higher in thetransverse direction is maintained. Thus, the production efficiency ofthe transversely stretched nonwoven fabric is increased, andmanufacturing unit cost of the transversely stretched nonwoven fabric asa web of large width is reduced. It is also possible to manufacture sucha transversely stretched nonwoven fabric as a web of large width withhigh strength and a high transverse stretch rate and to obtain atransversely stretched nonwoven fabric with wide applicability in termsof applications of the web.

[0024] The stretch suitable temperature depends on kinds of polymers offilaments, degree of polymerization, temperature of spinning, speed ofspinning, cooling condition and so on. In general, a stretch temperatureat which strength of the web after stretching rises most when a nonwovenfabric is stretched is adopted as the stretch suitable temperature. Arange of the stretch suitable temperature of polypropylene nonwovenfabric which is well-cooled in spinning is between 100° C. to 130° C. inthe hot wind stretching, preferably between 105° C. to 120° C. Thestretch suitable temperature of polyethylene telephthalate nonwovenfabric depends on a stretch speed mainly, the stretch suitabletemperature is 80° C. to 95° C. at low speed and 95° C. to 105° C. athigh speed.

[0025] “unoriented filament” does not mean that the degree of molecularorientation is completely zero, it is possible to stretch the unorientedfilament 3 times wider or more at its stretch suitable temperature. Whenunoriented filament is shown with degree of molecular orientation whichwas measured with birefringence and so on, degree of orientation of aperfect orientation is 100% and “unoriented filament” refers to thefilament having degree of orientation of 10% or less.

[0026] According to one aspect of the method of manufacturing atransversely stretched nonwoven fabric of the present invention, amethod of manufacturing a transversely stretched nonwoven fabricparticularly suitable for a web comprising un-oriented filaments mainlymade of polyethylene terephthalate (PET) is provided as a manufacturingmethod which allows the web to be stretched transversely at a highstretch rate. In the manufacturing method, while an original webcomprising un-oriented filaments mainly made of polyethyleneterephthalate is heated by hot air to a temperature of 100° C. or higherand is moved at a line speed of 20 m/min or higher at the same time, theoriginal web is stretched 7 times wider or more in its transversedirection in total such that the original web has a tensile strength of132.5 mN/tex (1.5 g/d) in a transverse direction. According to themanufacturing method, when a transversely stretched nonwoven fabricmainly made of PET is manufactured, it is possible to manufacture atransversely stretched nonwoven fabric with a tensile strength of 132.5mN/tex (1.5 g/d) in the transverse direction and a transverse stretchrate of 7 or more. It is preferable to use an original web comprisingtransversely aligned filaments as the original web before the transversestretch. The use of such an original web for manufacturing thetransversely stretched nonwoven fabric enables high strength and a highstretch rate to be realized in the transversely stretched nonwovenfabric.

[0027] The transverse stretch apparatus of the present invention usesthe method of manufacturing the transversely stretch nonwoven fabricwith the two-step stretch as described above. In the transverse stretchapparatus, first, an original web comprising un-oriented filaments isheated by first heating means to a temperature higher than its stretchsuitable temperature by 5° C. or more. The heated original web isstretched 1.2 to 3 times wider in its transverse direction by firststretch means. This causes the filaments of the original web to bestretched with almost no molecular orientation of the filamentsinvolved. At this point, the strength of the original web is notincreased yet. Next, the original web stretched 1.2 to 3 times wider inthe transverse direction is heated to the stretch suitable temperatureby second heating means, and is further stretched transversely by secondstretch means at the stretch suitable temperature. This results in atransversely stretched nonwoven fabric made of the original webstretched 7 times wider or more in the transverse direction in total ascompared with the state before the stretch by the first stretch means.Such a transverse stretch apparatus can be used to transversely stretchthe original web at a high rate at the stretch suitable temperaturethereof, and to obtain a tensile strength of the transversely stretchednonwoven fabric in the transverse direction equal to or higher than thatin normal stretch at the stretch suitable temperature. The transversestretch apparatus of performing such two-stretch provides, as a web oflarge width, a transversely stretched nonwoven fabric stretched at ahigh rate of 7 or more while a high tensile strength of 132.5 mN/tex(1.5 g/d) or higher in the transverse direction is maintained. Thus, theproduction efficiency of the transversely stretched nonwoven fabric isincreased, and manufacturing unit cost of the transversely stretchednonwoven fabric as a web of large web is reduced. Since such atransversely stretched nonwoven fabric can be manufactured as a web oflarge width with high strength and a high transverse stretch rate, it isalso possible to obtain a transversely stretched nonwoven fabric withwide applicability in terms of applications of the web.

[0028] In addition, first preheat means may be provided for preheatingthe original web by blowing hot air toward the original web such thatthe hot air passes through the original web before the heating of theoriginal web by the first heating unit.

[0029] Second preheat means may also be provided for heating theoriginal web by blowing hot air toward the original web such that thehot air passes through the original web before the original webstretched transversely by the first stretch means is heated by thesecond heating unit to its stretch suitable temperature.

[0030] The heating unit of the present invention heats the original webby hot air before the original web is transversely stretched and has anet member for supporting the original web at the heating by the hotair. The heating unit is provided, for example, for a transverse stretchapparatus for manufacturing a transversely stretched nonwoven fabric bytransversely stretching an original web. When the original web is heatedby the heating unit, hot air is blown toward the original web such thatthe hot air passes through the original web. At this point, the originalweb is supported on the net member by said net member contacting thesurface of the original web opposite to the side on which the hot air isblown in the portion in which the hot air is blown. At least part of thehot air through the original web further passes through the net member.Thus, deformation of the original web such as expansion thereof due tothe hot air is prevented. Since at least part of the hot air through theoriginal web further passes through the net member, the air contained inthe original web, or the air present in the gaps between the filamentsforming the original web is replaced with the air at a high temperaturefor heating the original web. Thus, the original web can be quickly anduniformly heated to an intended stretch temperature to stretch theoriginal web. As the net member, a mesh roll of hollow cylindrical shaperotatably supported and having a plurality of through holes formed inits wall, or a mesh conveyor belt supported movably in one direction canbe used.

[0031] The above and other objects, features and advantages of thepresent invention will become apparent from the following descriptionwith reference to the accompanying drawings which illustrate examples ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032]FIG. 1 is a sectional view showing a two-step transverse stretchapparatus which is a first embodiment of a transverse stretch apparatusof the present invention;

[0033]FIG. 2 is a plan view showing a spinning nozzle for forming anoriginal web for use in manufacturing a transversely stretched nonwovenfabric with the two-step transverse stretch apparatus shown in FIG. 1;

[0034]FIG. 3 is a diagram showing part of a manufacturing apparatususing the spinning nozzle shown in FIG. 2, viewed from the side;

[0035]FIG. 4 is a diagram showing part of the manufacturing apparatususing the spinning nozzle shown in FIG. 2, viewed from the front;

[0036]FIG. 5 is a perspective view showing the configuration of a firsttransverse stretch unit shown in FIG. 1;

[0037]FIG. 6 is a perspective view showing the configuration of a secondtransverse stretch unit shown in FIG. 1;

[0038]FIG. 7A is a diagram showing the interior of a transverse stretchapparatus of a second embodiment of the present invention, viewed fromthe top; and

[0039]FIG. 7B is a diagram showing the interior of the transversestretch apparatus shown in FIG. 7A, viewed from the side.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] In the present invention, “a longitudinal direction” used fordescribing an alignment direction of filaments in a nonwoven fabric, astretch direction and the like refers to the feeding direction of thenonwoven fabric in manufacturing the nonwoven fabric, while “atransverse direction” refers to a direction perpendicular to thelongitudinal direction, i.e., a width direction of the nonwoven fabric.For tensile strength of the nonwoven fabric, while JIS (JapaneseIndustrial Standards) L1096 employs representation of breaking strengthas a breaking load per 5 centimeters, the present invention employsrepresentation of tensile strength as strength per tex (mN/tex) withconversion from the weight of a nonwoven fabric to fineness (tex) sincenonwoven fabrics of various basis weights have been tested. Forreference, strength per denier (d) is also shown.

[0041] First Embodiment

[0042] Referring to FIG. 1, there is shown two-step transverse stretchapparatus 21, which is a transverse stretch apparatus of a firstembodiment of the present invention, comprising preheat unit 22, firsttransverse stretch unit 23, preheat unit 24, and second transversestretch unit 25. Preheat unit 22 is arranged upstream in the movingdirection of original web 1 used for manufacturing a transverselystretched nonwoven fabric. Preheat unit 22, first transverse stretchunit 23, preheat unit 24, and second transverse stretch unit 25 arealigned in this order along the moving direction of original web 1.Original web 1 is stretched 7 times wider or more in its transversedirection in total by two-step transverse stretch apparatus 21. Originalweb 1 before stretch with two-step transverse stretch apparatus 21comprises un-oriented filaments having many components thereof alignedtransversely.

[0043] Each of first transverse stretch unit 23 and second transversestretch unit 25 is a transverse stretch unit of pulley type which is anexample of a stretch apparatus preferable for transversely stretchingsuch original web, 1. Each of first transverse stretch unit 23 andsecond transverse stretch unit 25 is provided with a pair of pulleys anda pair of circulating belts for transversely stretching original web 1.Original web 1 is manufactured by scattering filaments discharged from aspinning nozzle with air such that many of the un-oriented filaments arealigned transversely. In first transverse stretch unit 23, original web1 is stretched 1.5 to 3 times wider in its transverse direction at atemperature higher than its stretch suitable temperature by 5° C. ormore. The step in first transverse stretch unit 23 is referred to aspreliminary stretch. In second transverse stretch unit 25, original web1 after the transverse stretch in first transverse stretch unit 23 isfurther stretched transversely such that original web 1 is stretched 7times wider or more in the transverse direction in total as comparedwith the state before the stretch in first transverse stretch unit 23.The step in second transverse stretch unit 25 is referred to as mainstretch. The stretch suitable temperature of original web 1 refers to atemperature suitable for stretch at which a desired strength of originalweb 1 in a transverse direction is obtained in transversely stretchingoriginal web 1. The main stretch in second transverse stretch unit 25 isperformed for the purpose of achieving strength of original web 1 in atransverse direction in transversely stretching original web 1.

[0044] Next, description is made for steps of manufacturing original web1 for use in manufacturing a transversely stretched nonwoven fabric intwo-step transverse stretch apparatus 21 shown in FIG. 1, with referenceto FIG. 2 to FIG. 4. FIG. 4 shows filaments which are spreadtransversely.

[0045] In manufacturing original web 1, as shown in FIG. 2 to FIG. 4,molten liquid 39 of filaments which are to form original web 1 isdischarged downward from discharge port 38 of spinning nozzle 34. Sixair holes 30 opened with slight inclination are provided arounddischarge port 38. Normally, three to eight air holes 30 are provided.Air flows ejected from respective air holes 30 intersect molten liquid39 discharged from discharge port 38 in a range from several to ten andseveral centimeters away from discharge port 38. Molten liquid 39intersecting the air flows from air holes 30 is rotated in a spiralabove screen mesh 32 which is of strip shape and runs in one directionindicated by arrow A shown in FIG. 3.

[0046] Other air holes 31 a, 31 b are provided below discharge port 38and air holes 30. Air holes 31 a, 31 b jet air flows toward thedirection perpendicular to the running direction of screen mesh 32 suchthat the air flows from air holes 31 a, 31 b intersect below dischargeport 38. The air flows jetted from air holes 31 a, 31 b collide witheach other below discharge port 38, and the colliding air flows spreadperpendicularly to the running direction of screen mesh 32. As a result,the jet of the spread air causes the discharged filaments rotating in aspiral to be sprayed perpendicularly to the running direction of screenmesh 32. Thereafter, the sprayed filaments are accumulated on screenmesh 32 running below them with many of the components alignedtransversely, thereby forming original web 1 serving as a nonwovenfabric with the filaments mainly aligned transversely. Typically, singlespinning nozzle 34 sprays molten liquid 39 in a width of 100 to 350 mm.

[0047] Next, description is made for each unit constituting two-steptransverse stretch apparatus 21 shown in FIG. 1.

[0048] In preheat unit 22 as a heating unit for preheating original web1, a pair of mesh rolls 4 a, 4 b which is a net-like member, and hot airblow ports 5 a, 5 b are disposed within housing 13 a. Hot air blow port5 a corresponds to mesh roll 4 a, while hot air blow port 5 bcorresponds to mesh roll 4 b. Preheat unit 22 is provided with a hot airproducing unit, not shown, for producing hot air which is dischargedfrom hot air blow ports 5 a, 5 b. The hot air producing unit, hot airblow ports 5 a, 5 b, mesh rolls 4 a, 4 b, and the like constitutepreheat unit 22 serving as first preheat means. The hot air in preheatunit 22 preheats original web 1 before original web 1 is moved to firsttransverse stretch unit 23.

[0049] Introduction port 14 is formed for introducing original web 1into housing 13 a in the wall opposite to first transverse stretch unit23 in housing 13 a of preheat unit 22. Cross guide 2 is arranged nearintroduction port 14 outside housing 13 a. Cross guide 2 is provided forfeeding original web 1 such that original web 1 is introduced straightinto housing 13 a, not into housing 13 a with a bend in its movingdirection. Original web 1 is moved to mesh rolls 4 a, 4 b through crossguide 2 and turn roll 3 a in housing 13 a.

[0050] Each of mesh rolls 4 a, 4 b is rotatably supported. As originalweb 1 wound around mesh rolls 4 a, 4 b is moved, the movement oforiginal web 1 causes mesh rolls 4 a, 4 b to be rotated. The pair ofmesh rolls 4 a, 4 b is provided for supporting original web 1 in heatingoriginal web 1 with hot air. When original web 1 is heated in mesh rolls4 a, 4 b, the hot air is blown on original web 1 such that the hot airpasses through original web 1. At this time, mesh rolls 4 a, 4 b supportoriginal web 1 to prevent deformation of original web 1 such asexpansion due to the hot air. Each of mesh rolls 4 a, 4 b has a hollowcylindrical shape and a mesh wall formed by providing a plurality ofthrough holes in the wall, for example. Original web 1 introduced intohousing 13 a is moved to first transverse stretch unit 23 after it iswound around part of each of mesh rolls 4 a, 4 b.

[0051] When part of original web 1 is wound around mesh roll 4 a, thehot air from hot air blow port 5 a is blown toward the portion oforiginal web 1 in contact with mesh roll 4 a. The hot air from hot airblow port 5 a passes through original web 1 and heats original web 1. Atthis point, the air within original web 1, i.e., the air present in thegap between the filaments constituting original web 1 is replaced withthe air at a high temperature from hot air blow port 5 a. This enablesquick and uniform heating of original web 1.

[0052] Mesh roll 4 a supports original web 1 by contacting the surfaceof original web 1 opposite to the side on which the hot air from hot airblow port 5 a is blown in the portion in which the hot air is blown. Thehot air through original web 1 passes through the through holes in thewall of mesh roll 4 a and flows into mesh roll 4 a. This preventsoriginal web 1 from being deformed due to the hot air or from moving.Exhaust box 10 a is disposed within mesh roll 4 a. Of the hot air fromhot air blow port 5 a, the hot air passing through original web 1 andthe through holes in the wall of mesh roll 4 a and flowing into meshroll 4 a is sucked through exhaust box 10 a.

[0053] Similarly, when part of original web 1 is wound around mesh roll4 b, the hot air from hot air blow port 5 b is blown on the portion oforiginal web 1 in contact with mesh roll 4 b. In this manner, the hotair from hot air blow port 5 b heats original web 1. Also in this case,mesh roll 4 b supports original web 1 by contacting the surface oforiginal web 1 opposite to the side on which the hot air from hot airblow port 5 b is blown in the portion in which the hot air is blown. Thehot air through original web 1 passes through the through holes in thewall of mesh roll 4 b and flows into mesh roll 4 b. This preventsoriginal web 1 from being deformed due to the hot air or from moving.

[0054] Exhaust box 10 b is disposed within mesh roll 4 b. Of the hot airfrom hot air blow port 5 b, the hot air passing through original web 1and the through holes in the wall of mesh roll 4 b and flowing into meshroll 4 b is sucked through exhaust box 10 b. The hot air sucked throughexhaust boxes 10 a, 10 b is discharged to the outside of housing 13 athrough a ventilation pipe.

[0055] Preheat unit 22 for passing the hot air through original web 1 asdescribed above employs mesh rolls 4 a, 4 b, i.e., cage roll ofcylindrical shape. On the other hand, in preheat unit 22, anothereffective method is that a web is carried and moved on a conveyorrunning in a plane such that the hot air passes through the web fromabove the conveyor to preheat the web.

[0056] Next, the configuration of first transverse stretch unit 23 shownin FIG. 1 is described with reference to FIGS. 1 and 5.

[0057] As shown in FIG. 5, first transverse stretch unit 23 serving asfirst stretch means comprises housing 13 b, a pair of left and rightstretch pulleys 6 a, 6 b surrounded by housing 13 b, circulating belts 8a, 8 b, and the like. First transverse stretch unit 23 is provided witha drive for rotating stretch pulleys 6 a, 6 b. Original web 1 isstretched 1.2 to 3 times wider in its transverse direction by firsttransverse stretch unit 23 at a temperature higher than its stretchsuitable temperature by 5° C. or more. The pair of left and rightstretch pulleys 6 a, 6 b have the same peripheral speed and arrangedsymmetrically about the center line such that the outer peripheries ofthe paired left and right stretch pulleys 6 a, 6 b have a trackgradually widening from upstream to downstream in the moving directionof original web 1, i.e., a gradually widening track.

[0058] Each of the paired stretch pulleys 6 a, 6 b has a belt grooveformed on its outer periphery. Part of circulating belt 8 a is fitted tothe belt groove of stretch pulley 6 a, while part of circulating belt 8b is fitted to the belt groove of stretch pulley 6 b. Circulating belt 8a (or rope) is stretched by rollers 7 a to 7 d such that part ofcirculating belt 8 a circulates on the track of the peripheral surfaceof stretch pulley 6 a in the gradually widening track formed by the pairof stretch pulleys 6 a, 6 b. Circulating belt 8 b (or rope) is stretchedby rollers 7 e to 7 h such that part of circulating belt 8 b circulateson the track of the peripheral surface of stretch pulley 6 b in thegradually widening track.

[0059] In such first transverse stretch unit 23, original web 1comprising un-oriented filaments from preheat unit 22 passes throughturn rolls 3 b, 3 c in housing 13 b and is introduced to the portionwhere the space between stretch pulleys 6 a and 6 b is the narrowest inthe paired stretch pulleys 6 a and 6 b. Original web 1 introduced frompreheat unit 22 into stretch pulleys 6 a, 6 b is carried with its oneedge portion in a transverse direction held between the belt groove ofstretch pulley 6 a and circulating belt 8 a and the other edge portionheld between the belt groove of stretch pulley 6 b and circulating belt8 b. In this manner, original web 1 is moved with both edge portions inits width direction sandwiched between stretch pulleys 6 a, 6 b andcirculating belts 8 a, 8 b. At this point, original web 1 is stretched1.2 to 3 times wider in the transverse direction by pulling both edgeportions of original web 1 on the gradually widening track formed bystretch pulleys 6 a, 6 b such that the distance between both edgeportions is increased. Transversely stretched original web 1 comes awayfrom stretch pulleys 6 a, 6 b and circulating belts 8 a, 8 b at theposition where the track of stretch pulleys 6 a, 6 b is the widest.Original web 1 leaving stretch pulleys 6 a, 6 b is moved outside housing13 b through turn roll 3 d in housing 13 b. Original web 1 stretched 1.2to 3 times wider in the transverse direction in first transverse stretchunit 23 in this manner is moved to preheat unit 24.

[0060] Housing 13 b is provided with hot air blow port 11 at the bottom.In addition, hot air blow port 5 c is disposed near upstream in themoving direction of original web 1 in the portion of original web 1 heldat both edge portions by stretch pulleys 6 a, 6 b and circulating belts8 a, 8 b. Hot air blow port 5 c is provided for blowing hot air on theupstream portion of original web 1 in the moving direction thereofwithin housing 13 b. These hot air blow ports 11, 5 c, a hot airproducing unit for producing hot air which is discharged from hot airblow ports 11, 5 c and the like constitute a heating unit serving asfirst heating means. The heating unit heats original web 1 in housing 13b to a temperature higher than its stretch suitable temperature by 5° C.or more.

[0061] Hot air blow port 11 is provided for blowing hot air on originalweb 1 from the outside of housing 13 b through the space between stretchpulleys 6 a and 6 b within housing 13 b. Hot air blow port 11 dischargeshot air into housing 13 b such that the hot air from hot air blow port11 passes through original web 1. In this manner, the hot air blown onoriginal web 1 is such that the hot air from hot air blow port 11 passesthrough original web 1 increases the thermal efficiency in heatingoriginal web 1.

[0062] Hot air blow port 5 c also discharges hot air toward original web1 such that the hot air therefrom passes through original web 1. The hotair from each of hot air blow ports 11, 5 heats original web 1 to atemperature higher than its stretch suitable temperature by 5° C. ormore.

[0063] Exhaust boxes 10 c, 10 d are provided on the side of original web1 opposite to hot air blow port 11 in the portion in which the hot airfrom hot air blow port 11 is blown. Exhaust box 10 c is disposed at aposition away from hot air blow port 5 c by a predetermined distancedownstream in the moving direction of original web 1. Exhaust box 10 dis disposed at a position away from exhaust box 10 c by a predetermineddistance downstream in the moving direction of original web 1. Exhaustboxes 10 c, 10 c suck the hot air passing through original web 1 of thehot air from hot air blow port 11. Exhaust box 10 e is also disposedbelow turn roll 3 d and sucks the air present in housing 13 b.Particularly, exhaust box 10 e sucks the air at a high temperatureflowing into a lower portion in housing 13 b from between stretchpulleys 6 a and 6 b.

[0064] In preheat unit 24 serving as a heating unit for preheatingoriginal web 1 before original web 1 is stretched by second transversestretch unit 25, mesh conveyor mesh belt 9 which is a net-like member isdisposed within housing 13 c. Conveyor mesh belt 9 is stretched by fourturn rolls 3 e and is supported to run in one direction. Conveyor meshbelt 9 is provided for supporting original web 1 when original web 1from first transverse stretch unit 23 is heated by hot air in housing 13c. Hot air is blown on original web 1 such that the hot air passesthrough original web 1 in heating original web 1 on conveyor mesh belt9. At this point, original web 1 is supported by conveyor mesh belt 9 toprevent deformation of original web 1 such as expansion due to the hotair, and original web 1 is carried toward second transverse stretch unit25. When the hot air is blown on original web 1 on conveyor mesh belt 9,the hot air passing through original web 1 further passes through holesin conveyor mesh belt 9.

[0065] A plurality of hot air blow ports 5 d are disposed in line alongthe moving direction of original web 1 above the portion of original web1 on conveyor mesh belt 9. A hot air producing unit for producing hotair which is discharged from hot air blow ports 5 d, a plurality of hotair blow ports 5 d, conveyor mesh belt 9 and the like constitute preheatunit 24 serving as second preheat means. A plurality of suction boxes 10e are disposed corresponding to respective hot air blow ports 5 d withinconveyor mesh belt 9.

[0066] The hot air from each of hot air blow ports 5 d is blown on theportion of original web 1 on conveyor mesh belt 9 such that the hot airpasses through original web 1. With this, the air within original web 1,i.e., the air present in the gaps between the filaments forming originalweb 1 is replaced with the air at a high temperature from hot air blowports 5 d. Thus, original web 1 is quickly and uniformly heated. Part ofthe hot air from hot air blow ports 5 d passes through original web 1and the through holes in conveyor mesh belt 9 and is sucked by suctionboxes 10 e.

[0067] Conveyor mesh belt 9 supports original web 1 by contacting thesurface of original web 1 opposite to the side on which the hot air fromhot air blow ports 5 d is blown in the portion in which the hot air isblown. This prevents original web 1 from being deformed and moving dueto the hot air. The portion of original web 1 heated by preheat unit 24is moved into second transverse stretch unit 25.

[0068] Next, the configuration of second transverse stretch unit 25shown in FIG. 1 is described with reference to FIGS. 1, 6.

[0069] As shown in FIG. 6, the mechanism of second transverse stretchunit 25 serving as second stretch means is similar to that of firsttransverse stretch unit 23 for transversely stretching original web 1.Second transverse stretch unit 25 comprises a pair of left and rightstretch pulleys 6 c, 6 d for transversely stretching original web 1, andcirculating belts 8 c, 8 d corresponding to the respective stretchpulleys. Second transverse stretch unit 25 differs from first transversestretch unit 23 in the stretch rate of original web 1 in a transversedirection and a heating unit for heating original web 1 in secondtransverse stretch unit 25.

[0070] In second transverse stretch unit 25, the pair of left and rightstretch pulleys 6 c, 6 d, circulating belt 8 c corresponding to stretchpulley 6 c, and circulating belt 8 d corresponding to stretch pulley 6 dare arranged within housing 13 d. Second transverse stretch unit 25 isalso provided with a drive for rotating stretch pulleys 6 c, 6 d.Original web 1 which has been transversely stretched by first transversestretch unit 23 is further stretched transversely by second transversestretch unit 25 at its stretch suitable temperature. The additionalstretch of original web 1 by second transverse stretch unit 25 causesoriginal web 1 to be stretched transversely at a rate of 7 or more intotal as compared with the state before the stretch by first transversestretch unit 23.

[0071] The pair of left and right stretch pulleys 6 c, 6 d have the sameperipheral speed and arranged symmetrically about the center line suchthat the outer peripheries of the paired left and right stretch pulleys6 c, 6 d have a track gradually widening from upstream to downstream inthe moving direction of original web 1, i.e., a gradually wideningtrack.

[0072] Each of the pair of stretch pulleys 6 c, 6 d has a belt grooveformed on its peripheral surface. Part of circulating belt 8 c is fittedto the belt groove of stretch pulley 6 c, while part of circulating belt8 d is fitted to the belt groove of stretch pulley 6 d. Circulating belt8 c (or rope) is stretched by rollers 7 i to 7 l such that part ofcirculating belt 8 c circulates on the track of the peripheral surfaceof stretch pulley 6 c in the gradually widening track formed by the pairof stretch pulleys 6 c, 6 d. Circulating belt 8 d (or rope) is stretchedby rollers 7 m to 7 p such that part of circulating belt 8 d circulateson the track of the peripheral surface of stretch pulley 6 d in thegradually widening track.

[0073] The width at the beginning of the gradually widening track formedby stretch pulleys 6 c, 6 d is the same as that at the end of thegradually widening track formed by stretch pulleys 6 a, 6 b in firsttransverse stretch unit 23. Stretch pulleys 6 c, 6 d are disposedopposite to each other in V shape such that the width at the end of thegradually widening track of stretch pulleys 6 c, 6 d is larger than thewidth at the beginning thereof. In this manner, stretch pulleys 6 c, 6 dconstitute the gradually widening track for further stretchingtransversely original web 1 supplied from first transverse stretch unit23.

[0074] In second transverse stretch unit 25, original web 1 from preheatunit 24 is introduced through turn roll 3 f in housing 13 d to theportion where the space between stretch pulleys 6 c and 6 d is thenarrowest in the paired stretch pulleys 6 c, 6 d. Original web 1introduced from preheat unit 24 onto stretch pulleys 6 c, 6 d is carriedwith both edge potions in its width direction being held between stretchpulley 6 c and circulating belt 8 c, and between stretch pulley 6 d andcirculating belt 8 d, and is transversely stretched with the trackformed by stretch pulleys 6 c, 6 d. As described above, secondtransverse stretch unit 25 transversely stretches original web 1 suchthat original web 1 is stretched transversely at a rate of 7 or more intotal as compared with the state before original web 1 is transverselystretched by first transverse stretch unit 23. As a result, transverselystretched nonwoven fabric 12 formed from original web 1 stretched 7times wider or more in the transverse direction in total ismanufactured. Transversely stretched nonwoven fabric 12 thusmanufactured comes away from stretch pulleys 6 c, 6 d and circulatingbelts 8 c, 8 d at the position where the track of stretch pulleys 6 c, 6d has the largest width, and is moved to the outside of housing 13 dthrough turn roll 3 g in housing 13 d.

[0075] As described above, in first transverse stretch unit 23 forperforming the preliminary stretch, the hot air from hot air blow port11 is blown toward original web 1 such that the hot air passes throughoriginal web 1 to heat original web 1. On the other hand, in secondtransverse stretch unit 25 for performing the main stretch, hot air isblown on original web 1 along the flow of original web 1 to heatoriginal web 1. Three hot air blow ports 5 e to 5 g are provided insidehousing 13 d of second transverse stretch unit 25. These hot air blowports 5 e to 5 g, a hot air producing unit for producing hot air whichis discharged from hot air blow ports 5 e to 5 g and the like constitutea heating unit serving as second heating means. The heating means heatsoriginal web 1 within housing 13 d to its stretch suitable temperature.

[0076] Hot air blow port 5 e is disposed near turn roll 3 f and on theside of original web 1 facing stretch pulleys 6 c, 6 d. Hot air is blownfrom hot air blow port 5 e toward original web 1 such that the hot airdischarged from hot air blow port 5 e flows from the proximity of turnroll 3 f in the moving direction of original web 1 along the surface oforiginal web 1 on the sides of stretch pulleys 6 c, 6 d. Suction box 10i is disposed in a lower portion within housing 13 d. Of the hot airdischarged from hot air blow port 5 e and flowing along the surface oforiginal web 1 on the sides of stretch pulleys 6 c, 6 d, the hot airflowing into the proximity of the bottom within housing 13 d is suckedby suction box 10 i.

[0077] Hot air blow port 6 f, is disposed near upstream in the movingdirection of original web 1 in the portion where both edge portions oforiginal web 1 are held between stretch pulleys 6 c, 6 d and circulatingbelts 8 c, 8 d, and on the side of original web 1 facing circulatingbelts 8 c, 8 d. Hot air is obliquely blown from hot air blow port 6 f,toward the surface of original web 1 such that the hot air from hot airblow port 5 flows upstream in the moving direction of original web 1.

[0078] Hot air blow port 5 g is disposed near the upper part of originalweb 1 in the portion where its both edge portions are held betweenstretch pulleys 6 c, 6 d and circulating belts 8 c, 8 d, and on the sideof original web 1 facing circulating belts 8 c, 8 d. Hot air isdischarged from hot air blow port 5 g such that the hot air from hot airblow port 5 g flows downstream in the moving direction of original web 1along the surface of original web 1.

[0079] Suction box 10 f is disposed near hot air blow port 5 g above thesurface of original web 1 facing circulating belts 8 c, 8 d withinhousing 13 d. Suction box 10 f sucks the air in the space upstream fromhot air blow port 5 g in the moving direction of original web 1. Suctionboxes 10 g, 10 h are disposed with a predetermined interval between themabove the surface of original web 1 facing circulating belts 8 c, 8 dwithin housing 13 d downstream from hot air blow port 5 g in the movingdirection of original web 1. Suction boxes 10 g, 10 h sucks the air inthe space downstream from hot air blow port 5 g in the moving directionof original web 1.

[0080] As described above, in first transverse stretch unit 23, the hotair from hot air blow port 11 is blown on original web 1 such that thehot air passes through original web 1 to heat original web 1, while insecond transverse stretch unit 25, the hot air is blown on original web1 along the flow of original web 1 to heat original web 1. However, theconfigurations for heating original web 1 may be exchanged in firsttransverse stretch unit 23 and second transverse stretch unit 25.Specifically, in first transverse stretch unit 23, original web 1 may beheated by blowing hot air on original web 1 along the flow of originalweb 1. In second transverse stretch unit 25, original web 1 may beheated by a hot air passing method in which hot air is blown from beloworiginal web 1 such that the hot air passes through original web 1 andthe hot air is sucked above original web 1. Alternatively, original web1 may be heated by the hot air passing method both in first transversestretch unit 23 and in second transverse stretch unit 25, or originalweb 1 may be heated by blowing hot air along the flow of original web 1in these units.

[0081] In addition, while original web 1 is heated by hot air in firsttransverse stretch unit 23 and second transverse stretch unit 25 in theembodiment, original web 1 may be heated by warm water, infraredradiation or the like, instead of hot air.

[0082] As described above, in two-step transverse stretch unit 21 of theembodiment, original web 1 made of unoriented filaments is heated bypreheat unit 22 and the heating unit in first transverse stretch unit 23to a temperature higher than the stretch suitable temperature by 5° C.or more, and heated original web 1 is stretched 1.2 to 3 times wider inthe transverse direction in first transverse stretch unit 23. In thispreliminary stretch step, the filaments forming original web 1 arestretched with almost no molecular orientation involved. At this point,the strength of the original web is not increased yet. Next, originalweb 1 stretched 1.2 to 3 times wider in the transverse direction infirst transverse stretch unit 23 is further heated to the stretchsuitable temperature by preheat unit 24 and the heating unit in secondtransverse stretch unit 25, and the heated original web 1 is furtherstretched transversely at the stretch suitable temperature in secondtransverse stretch unit 25. This main stretch step manufacturestransversely stretched nonwoven fabric 12 made of original web 1stretched 7 times wider or more in the transverse direction in total ascompared with the state before the stretch in first transverse stretchunit 23. The main stretch step involves molecular orientation of thefilaments forming original web 1. The step can allow a tensile strengthof 132.5 mN/tex (1.5 g/d) in the transverse direction or higher fortransversely stretched nonwoven fabric 12 made of stretched original web1.

[0083] The diameter of the fiber of the filaments forming transverselystretched nonwoven fabric 12 is 1 μm or more and 20 μm or less forproviding transversely stretched nonwoven fabric 12 with properties as acloth in terms of texture. The diameter of the fiber is preferably 3 μmor more and 15 μm or less, and most preferably 5 μm or more and 12 μm orless. To obtain the diameter, it is necessary that the diameter of thefiber of the filaments forming original web 1 is 30 μm or less,desirably 20 μm or less. When the diameter of the fiber of the filamentsof transversely stretched nonwoven fabric 12, i.e., the diameter of thefiber of the filaments after the stretch is 1 μm or less, the strengthof transversely stretched nonwoven fabric 12 is not obtained in manycases.

[0084] A total stretch rate of the web in two-step transverse stretchapparatus 21 is 7 or higher and 20 or lower, preferably 8 or higher and15 or lower, and most preferably 9 or higher and 12 or lower. Forstretching original web 1, 20 times wider or more in the transversedirection in total, it is necessary to increase the stretch rate infirst transverse stretch unit 23, i.e., the stretch rate in thepreliminary stretch. However, the experimental results have shown thatsufficient strength of the web after the main stretch is not obtained ifthe stretch rate in the preliminary stretch is too high.

[0085] With manufacture of transversely stretched nonwoven fabric 12using such two-step transverse stretch apparatus 21, original web 1 istransversely stretched at a high rate at the stretch suitabletemperature, and it is possible to obtain a tensile strength oftransversely stretched nonwoven fabric 12 in the transverse directionequal to or higher than that in normal stretch at the stretch suitabletemperature. As a result, the transverse stretch apparatus forperforming the two-step stretch can manufacture, as a web of largewidth, transversely stretched nonwoven fabric 12 stretched at a highstretch rate of 7 or more while a high tensile strength of 132.5 mN/tex(1.5 g/d) or higher is ensured in the transverse direction. Thus, theproduction efficiency of transversely stretched nonwoven fabric 12 canbe enhanced to reduce the manufacturing unit cost of transverselystretched nonwoven fabric 12 as a web of large width. In addition, sincetransversely stretched nonwoven fabric 12 at a high stretch rate in thetransverse direction can be manufactured with such high strength as aweb of large width, it is possible to obtain transversely stretchednonwoven fabric 12 with wide applicability in terms of applications ofthe web.

[0086] Second Embodiment

[0087] A transverse stretch apparatus of a second embodiment of thepresent invention employs a so-called tenter frame in which both edgeportions of an original web in a transverse direction are held in oneplane to stretch transversely the original web.

[0088] As shown in FIGS. 7A and 7B, in the transverse stretch apparatusof the embodiment, a pair of chains 56 a, 56 b running for transverselystretching original web 1 is disposed inside housing 53. The space inhousing 53 is divided into two chambers, i.e., high temperature heatingchamber 58 and low temperature heating chamber 59, by inner wall 54extending perpendicularly to a horizontal direction. High temperatureheating chamber 58 corresponds to a chamber of first transverse stretchunit 43 for performing preliminary stretch, while low temperatureheating chamber 59 corresponds to a chamber of second transverse stretchunit 45 for performing main stretch.

[0089] Introduction port 55 a is formed substantially at the center ofthe side wall facing inner wall 54 of the side wall forming hightemperature heating chamber 58 of housing 53 for feeding original web 1into high temperature heating chamber 58. Opening portion 54 a is alsoformed in inner wall 54 for feeding original web 1 after the preliminarystretch in high temperature heating chamber 58 into low temperatureheating chamber 59 from high temperature heating chamber 58. Inaddition, introduction port 55 b is formed in the side wall facing innerwall 54 of the side walls forming low temperature heating chamber 59 ofhousing 53. Transversely stretched web 12 manufactured by performing themain stretch on original web 1 in low temperature heating chamber 59 isfed from the inside of low temperature heating chamber 59 to the outsidethereof through introduction port 55 b. Original web 1 is moved in onedirection such that original web 1 passes through high temperatureheating chamber 58 and low temperature heating chamber 59 in this order.Original web 1 is stretched in its width direction or transversely inhigh temperature heating chamber 58 and low temperature heating chamber59.

[0090] The transverse stretch apparatus of the embodiment furthercomprises a heating unit serving as first heating means for heatingoriginal web 1 in high temperature heating chamber 58 to a temperaturehigher than its stretch suitable temperature by 5° C. or more, and aheating unit serving as second heating means for heating original web 1in low temperature heating chamber 59 to its stretch suitabletemperature. In such a transverse stretch apparatus, the section fromthe end on the side of introduction port 55 a to inner wall 54 in theapparatus provides first transverse stretch unit 43 for performing thepreliminary stretch on original web 1 at a temperature higher than thestretch suitable temperature of original web 1. The section from innerwall 54 to the end on the side of introduction port 55 b provides secondtransverse stretch unit 45 for performing main stretch on original web 1at the stretch suitable temperature.

[0091] Chains 56 a, 56 b are arranged perpendicularly to the movingdirection of original web 1 and in parallel to original web 1, and bothchains 56 a and 56 b run within one plane substantially parallel tooriginal web 1. Chain 56 a is stretched by chain wheel 57 a disposed inhigh temperature heating chamber 58 and chain wheels 57 b to 57 ddisposed in low temperature heating chamber 59. Chain 56 b is stretchedby chain wheel 57 e disposed in high temperature heating chamber 58 andchain wheels 57 f to 57 h disposed in low temperature heating chamber59.

[0092] Each of the portion between chain wheels 57 a and 57 b and theportion between chain wheels 57 a and 57 d in chain 56 a, and theportion between chain wheels 57 e and 57 f and the portion between chainwheels 57 e and 57 h in chain 56 b is inclined with respect to themoving direction of original web 1. Those portions in chains 56 a, 56 bare disposed within high temperature heating chamber 58 and lowtemperature heating chamber 59 through opening portion 54 a in innerwall 54. The portion between chain wheels 57 a and 57 b in chain 56 aand the portion between chain wheels 57 e and 57 f in chain 56 b areopposed to each other such that the space between those portions isgradually increased downstream in the moving direction of original web1.

[0093] On the other hand, the portion between chain wheels 57 d and 57 cin chain 56 a and the portion between chain wheels 57 h and 57 g inchain 56 b run along a direction substantially parallel to the movingdirection of original web 1 such that those portions are opposed to eachother. Thus, the portions in chains 56 a, 56 b except the end portionsdownstream in the moving direction of original web 1 runs obliquely withrespect to the moving direction of original web 1 such that the spacebetween chains 56 a and 56 b is gradually increased downstream in themoving direction of original web 1.

[0094] As shown in FIG. 7B, a plurality of pins 52 extending upward fromthe top surface of chain 56 a are provided over the entire longitudinaldirection of chain 56 a. These pins 52 are provided for holding the edgeportion of original web 1 on the side of chain 56 a by penetrating theedge portion. Similarly, a plurality of pins extending upward from thetop surface of chain 56 b are provided over the entire longitudinaldirection of chain 56 b. These pins are provided for holding the edgeportion of original web 1 on the side of chain 56 b by penetrating theedge portion.

[0095] The pins each on chains 56 a, 56 b hold both edge portions oforiginal web 1 in its width direction, and simultaneously, the runningof chains 56 a, 56 b causes original web 1 to be moved. When originalweb 1 is moved by chains 56 a, 56 b in this manner, original web 1 isheated to a temperature higher than its stretch suitable temperature by5° C. or more and stretched 1.2 to 3 times wider in the transversedirection with chains 56 a, 56 b in high temperature heating chamber 58of first transverse stretch unit 43. In low temperature heating chamber59 of second transverse stretch unit 45, original web 1 is furtherstretched transversely at the stretch suitable temperature with theinclined portions of chains 56 a, 56 b.

[0096] Therefore, chains 56 a, 56 b, and the pins formed on the chainswhich hold both edge portions of original web 1 in first transversestretch unit 43 constitute first stretch means for stretching originalweb 1, 1.2 to 3 times wider in the transverse direction. Chains 56 a, 56b, and the pins formed on the chains which hold both edge portions oforiginal web 1 in second transverse stretch unit 45 constitute secondstretch means for further stretching transversely original web 1 toperform the main stretch. In this manner, original web 1 is transverselystretched by first transverse stretch unit 43 and second transversestretch unit 45, thereby stretching original web 1, 7 times wider ormore in the transverse direction in total as compared with the statebefore the stretch in first transverse stretch unit 43. These stepsresult in transversely stretched nonwoven fabric 12 made of original web1 transversely stretched and having a tensile strength in the transversedirection of 132.5 mN/tex (1.5 g/d) or higher.

[0097] In the embodiment, the portion between chain wheels 57 a and 57 bin chain 56 a, and the portion between chain wheels 57 e and 57 f inchain 56 b extend linearly. However, a chain wheel other than the chainwheels shown in FIGS. 7A and 7B may be newly added to the transversestretch apparatus for setting the stretch rate of original web 1 insecond transverse stretch unit 45 at a predetermined value with respectto the stretch rate of original web 1 in first transverse stretch unit43. Specifically, a chain wheel contacting the inner side or outer sideof chain 56 a is newly provided at a position near opening portion 54 abetween chain wheels 57 a and 57 d of chain 56 a, and a chain wheelcontacting the inner side or outer side of chain 56 b is newly providedat a position near opening portion 54 a between chain wheels 57 e and 57h of chain 56 b. These additional provisions allow setting of the ratioof the stretch rate in first transverse stretch unit 43 to the stretchrate in second transverse stretch unit 45 at a predetermined value.

[0098] While an apparatus for heating original web 1 is not shown inFIGS. 7A and 7B, original web 1 can be heated by hot air in thetransverse stretch apparatus of the embodiment similarly to the firstembodiment. As in the heating method used in first transverse stretchunit 23 of the first embodiment, hot air may be blown on original web 1such that the hot air passes through original web 1 and the hot air issucked through original web 1. Alternatively, as in the heating methodused in second transverse stretch unit 25 of the first embodiment, hotair may be blown on original web 1 along the moving direction oforiginal web 1. The method of passing hot air through original web 1 maybe used in one of first transverse stretch unit 43 and second transversestretch unit 45, and the method of blowing hot air along the movingdirection of original web 1 may be used in the other. Alternatively, oneof the methods of passing hot air through original web 1 and the methodof blowing hot air along the moving direction of original web 1 may beused both in first transverse stretch unit 32 and in second transversestretch unit 45.

[0099] In addition, in the transverse stretch apparatus of theembodiment, only one pair of chains 56 a, 56 b is used to provide firsttransverse stretch unit 43 for performing the preliminary stretch andsecond transverse stretch unit 45 for performing the main stretch.However, different pairs of chains may be used for the preliminarystretch and the main stretch, respectively. Specifically, chains 56 a,56 b shown in FIG. 7A and chain wheels 57 a to 57 h for supporting thechains may be used for the preliminary stretch, and another pair ofchains and another set of chain wheels may be used for the main stretch.Thus, two transverse stretch apparatuses of tenter frame with differentstretch rates may be arranged along the moving direction of original web1 to provide a transverse stretch apparatus for performing two-stepstretch. In this case, the two-step transverse stretch apparatus isconfigured such that, of the two transverse stretch apparatuses oftenter frame, the stretch apparatus upstream in the moving direction oforiginal web 1 is used for the preliminary stretch, and the stretchapparatus downstream in the moving direction is used for the mainstretch.

[0100] Various nonwoven fabric can be used as original web 1 for use inmanufacturing the transversely stretched nonwoven fabric in the presentinvention. Since original web 1 needs to realize both high strength oftransversely stretched nonwoven fabric 12 obtained by stretching the weband a high stretch rate of original web 1, a nonwoven fabric whichsatisfies the following conditions is particularly desirable.

[0101] First, it is necessary that the diameter of the filamentsconstituting original web 1 is 30 μm or less, desirably 20 μm or less.Transversely stretched nonwoven fabric 12 in the present invention,which requires properties as a cloth in terms of its strength andtexture, needs to be made of filaments with a diameter after stretchequal to or lower than 20 μm. To achieve this, the diameter of thefilaments of original web 1 before stretch must be equal to or lowerthan 30 μm.

[0102] Second, original web 1 needs to be made of filaments with almostno molecular orientation. This is because filaments which already havemolecular orientation are difficult to stretch further.

[0103] Thirdly, it is necessary that original web 1 is formed fromfilaments rapidly cooled at the spinning step and the filaments have astructure as close to amorphous as possible. This is because, ifcrystallization of the filaments progresses at the spinning step orlater step, the crystal needs to be destroyed for stretching thefilaments, resulting in susceptibility to stretch breaking of thefilaments.

[0104] Fourthly, it is necessary that original web 1 is a nonwovenfabric with filaments aligned transversely and the filaments extend overboth edges from one edge to the other edge in the width direction oforiginal web 1. This is because such transverse alignment of thefilaments is desirable to realize high strength and a high rate of atransversely stretched nonwoven fabric in typically used transversestretch means which holds both edges of a web in its width direction(transverse direction). However, if the filaments do not extend overboth edges from one edge to the other edge of original web 1, stretch oforiginal web 1 after partial bonding, later described, can be applied.

[0105] The present invention intends to obtain a transversely stretchedweb of large width at high rate stretch. It is difficult for prior artsto increase a stretch rate in transversely stretching an original web,and the stretch rate is, even if increased, 5 to 6 at the maximum. Assolving means for increasing the stretch rate, in the present invention,first, transverse stretch (preliminary stretch) is performed at astretch rate of 1.2 or higher and 3 or lower at a temperature higherthan a normal stretch suitable temperature by 5° C. or more, desirably10° C. or more for polyethylene terephthalate (PET), and by 20° C. ormore, desirably 40° C. or more for other polymer filaments such aspolypropylene (PP). Thereafter, transverse stretch (main stretch) isperformed in order to obtain strength of a nonwoven fabric after thetemperature of the nonwoven fabric is reduced to the normal stretchsuitable temperature. Such two-step transverse stretch consisting of thepreliminary stretch and main stretch can easily realize stretch at atransverse stretch rate of 7 or more in total, specifically at a rate of8 to 10, and can obtain a strength of the transversely stretched webafter the stretch equal to or higher than that of normal stretch. Thepreliminary stretch in such high rate stretch is stretch in which themolecules of the filaments flow with no molecular orientation, i.e.,flow stretch with almost no molecular orientation. In this preliminarystretch, the strength of the web is not increased yet. It is realizedfrom the experimental results that a stretch rate of 1.2 or lower in thepreliminary stretch does not lead to a high stretch rate in the mainstretch, while a stretch rate of 3 or higher results in a reduction inthe strength of the web.

[0106] Other Embodiments

[0107] As a method for allowing stretch at a high stretch rate besidesthe two-step transverse stretch method constituting the preliminarystretch and main stretch as described above, a method of manufacturing astretch web particularly suitable for an original web un-orientedcomprising filaments mainly made of PET was experimentally established.In the method, while an original web mainly made of PET was moved in ahot air temperature at 100° C. or higher, more desirably at 105° C. orhigher, at a line speed of 20 m/min or higher, more desirably at 30m/min, the original web was stretched 7 times wider or more in itstransverse direction in total. This enabled manufacture of atransversely stretched web, as a transversely stretched web made of PET,at a transverse stretch rate of 7 or more in total and with a transversetensile strength of 132.5 mN/tex (1.5 g/d) or higher. In the case of atemperature at which the original web is at 130° C. or higher, PETfilaments were melted, and a transverse tensile strength of 132.5 mN/tex(1.5 g/d) or higher could not be obtained for the web.

[0108] When an original web has a small width, a plurality of originalwebs of small width are arranged in parallel such that two adjacentoriginal webs are partially bonded to each other at the sides thereof inadvance. In this manner, the plurality of original webs are formed intoone sheet to constitute an original web of large width. The original webof large width formed from the partially bonded original webs is movedin one direction for transverse stretch. Such a method can provide bothhigh strength of the original web from the partially bonded points inthe original web of large width and large width of the original webbefore transverse stretch. In addition, it is also possible that aplurality of original webs are laminated one over another and the entirelaminated original webs are partially bonded, thereby allowing anoriginal web of large basis weight to be formed.

[0109] If attempts are made to perform the transverse stretch of a webat an industrial speed and to obtain a high rate and high strength, thetemperature of the web is not increased due to delay of heating of theair contained in the web, and uniform heating of the web cannot beperformed. Thus, as in two-step stretch apparatus 21 of the firstembodiment, it is necessary to uniformly heat original web 1 to anintended stretch temperature before original web 1 is introduced intofirst transverse stretch unit 23 or second transverse stretch unit 25.With this heating, the temperature of the web can be increased to auniform stretch temperature in first transverse stretch unit 23 or insecond transverse stretch unit 25 by replacing the air contained inoriginal web 1 with the air at a stretch temperature by hot air at thestretch temperature. A preheat unit which heats the web in this mannercan realize stretch at a high rate and high strength. Means forreplacing the air in the web allows the hot air to pass through the webwhen the web is carried by mesh web carrying means with airpermeability. Such replacing means can replace the air contained in theweb with the air at the stretch temperature.

[0110] The aforementioned carrying means include a mesh roll, a meshconveyor belt, or the like. The hot air passing through the carryingmeans and the web may be hot air sucked by suction means disposed on theside of the carrying means, or hot air blown on the web from the side ofthe carrying means. It is essential only that the hot air passes throughthe web.

[0111] Various conventional transverse stretch apparatuses for webs canbe used as a transverse stretch apparatus which can realize thetransverse stretch of the present invention. Conventional web stretchmeans include a tenter frame for use as a transverse stretch apparatusfor films, and means (U.S. Pat. No. 4,223,059) for transverselystretching webs between two combined groove rolls. In addition, a pulleytype stretch method described in Japanese Patent Publication No.36948/91 applied by the present applicant used in the first embodimentis effective.

[0112] For realizing the high rate stretch of the present invention,first, preliminary stretch is performed transversely at a hightemperature and at a low stretch rate. Since the preliminary stretch isperformed at a low rate, and the preliminary stretch requires noconsideration of an increase in temperature to a stretch temperature ifthe aforementioned preheat unit is used, the transverse stretch unit forperforming the preliminary stretch may be simple as one of means forrealizing the high rate stretch of the present invention. As such aunit, a groove roll type stretch apparatus or a pulley type stretch unitis effective.

[0113] Also in the main stretch after the preliminary stretch, thepulley type stretch apparatus which is a simplified stretch apparatusand has favorable operability is particularly suitable as the transversestretch apparatus.

[0114] While a stretch apparatus of tenter frame has disadvantages inthat it is expensive and requires a large floor area, it has anadvantage that a stretch temperature can be changed freely in a singlestretch apparatus. Therefore, the tenter stretch apparatus can beutilized in the implementation of the present invention, and in such acase, an original web is preliminarily stretched at a high temperaturein the initial stage of the stretch in the stretch apparatus, and then,the temperature of the original web is reduced to a stretch suitabletemperature for stretch.

[0115] The provision of a heat treatment zone for performing heattreatment on an original web after stretch is effective to enhance thestability of the web. Normally, an effective heat treatment zone isprovided such that heat treatment is performed on the original web withboth edges thereof being held after transverse stretch is completed.

[0116] While the hot air is typically used for heating required in thestretch of the present invention as described above, another heat mediummay be used in order to prevent oxidation or the like. Hot water andsteam are effective for the heating of the web due to fast heattransfer.

[0117] The stretch temperature of the web in the stretch step is heldconstant by passing a heat medium through the web, or flowing the heatmedium along the web.

[0118] While the present invention is directed basically to atransversely stretched nonwoven fabric and a method of manufacturing thesame, a stretch rate of the web depends on kinds of polymers offilaments constituting the web, spinning means or aligning means for theweb. However, a stretch rate is selected to allow a high degree oforientation and high strength of the web, which are the objects of thepresent invention, even with any kinds or means.

[0119] The stretch rate is derived with the following equation by usingmarks which are provided in the web before stretch at regular intervalsin the stretch direction.

stretch rate=(inter-mark length after stretch)/(inter-mark length beforestretch)

[0120] The stretch rate does not necessarily mean a stretch rate of eachof the filaments as in typical stretch of long fiber filament yarn.

[0121] As polymer serving as a strength member suitable for filamentsconstituting the transversely stretched nonwoven fabric of the presentinvention, thermoplastic resins such as polyethylene, polypropylene,polyester, polyamide, polyvinyl chloride base resin, polyurethane,fluorocarbon resin, or any of the denatured resins thereof may be used.In addition, resins for wet or dry spinning means such as polyvinylalcohol base resins, polyacrylonitrile resins or the like may be used.

[0122] The present invention can be used in mix spinning and conjugatespinning described in International Publication WO 96/17121 by thepresent applicant, and the like.

EXAMPLE 1

[0123] In Example 1, and Examples 2, 3, later described, the testresults of material properties are shown only for a transverse directionaccording to a test method for a long fiber filament nonwoven fabric inJIS L1096. In JIS L1096, breaking strength is represented with abreaking load per 5 centimeters. The following description employsrepresentation of strength per tex (mN/tex) with conversion from theweight of a nonwoven fabric to fineness (tex) since nonwoven fabrics ofvarious basis weights were tested. For reference, strength per denier(d) is also shown.

[0124] In Example 1, polypropylene obtained by degradation was spun withthe spinning apparatus described on the basis of FIG. 2 to FIG. 4 at anMFR (Melt Flow Rate) of 500 as a flow speed to form an original web witha width of 380 mm which was then transversely stretched. When originalweb 1 is transversely stretched, either two-step stretch apparatus 21 ofthe first embodiment or the transverse stretch apparatus of the tentertype of the second embodiment can be used. In transversely stretchingthe original web, each width of chuck portions at left and right edgesof the original web was set at 40 mm. Thus, the distance between thechucks immediately before the stretch of the original web of 380 mmwidth was 300 mm. The transverse stretch was performed on the portionbetween the two chucks on both sides of the original web, i.e., theportion corresponding to the area of 300 mm width except the chuckportions in the original web before the stretch. The following examplesalso employ the 40 mm width for the chuck portions on left and rightsides of the original web.

[0125] First, the aforementioned portions corresponding to the area of300 mm width except the chuck portions in the original web of 380 mmwidth was transversely stretched at a preliminary stretch temperature of135° C. and at a stretch rate of two for preliminary stretch in themanufacturing apparatus, thereby causing the original web to have awidth of approximately 680 mm in total. Next, the original web ofapproximately 680 mm width was transversely stretched at a stretchtemperature of 115° C. at a stretch rate of 5 for main stretch in themanufacturing apparatus, thereby obtaining a transversely stretchednonwoven fabric with a width of 2920 mm. The transverse stretch of theportion corresponding to the area of 600 mm width except the chuckportions in the original web of approximately 680 mm width at the mainstretch rate of 5 resulted in the width 2920 mm of the portion of thetransversely stretched nonwoven fabric, which is narrower than 3000 mm,because slight shrinkage was involved in the stretched portion. Thosesteps allowed the manufacture of the transversely stretched nonwovenfabric in strip shape at a total stretch rate of 10 in a transversedirection in the manufacturing apparatus, a tensile strength of 203.1mN/tex (2.3 g/d) in the transverse direction, and a width of 2920 mm(due to the slight shrinkage).

[0126] Typically, a stretch suitable temperature for a nonwoven fabricmade of rapidly cooled polypropylene is 90 to 100° C., and a maximumstretch rate for the polypropylene nonwoven fabric ranged from 5.5 to6.0 in that temperature range.

EXAMPLE 2

[0127] In Example 2, an original web with a width of 400 mm obtained bythe spinning apparatus described on the basis of FIG. 2 to FIG. 4 wastransversely stretched using a polyethylene telephthalate molten resinwith a limiting viscosity of 0.52. First, the original web of 400 mmwidth was transversely stretched at a preliminary stretch temperature of105° C. and at a stretch rate of 1.5 for preliminary stretch in themanufacturing apparatus. Thereafter, the original web was furtherstretched transversely at a main stretch temperature of 90° C. and at astretch rate of 6 for main stretch in the manufacturing apparatus.

[0128] Since this example also employed a width of 40 mm for chuckportions on left and right sides of the original web as described inExample 1, the distance between the chucks immediately before thestretch was 320 mm, and the transverse stretch was performed on theportion corresponding to the area of 320 mm width except the chuckportions in the original web before the stretch. Thus, when the portioncorresponding to the area of 320 mm except the chuck portions in theoriginal web of 400 mm width was transversely stretched at thepreliminary stretch rate of 1.5, the width of the resultant original webwas approximately 560 mm in total. The portion corresponding to the areaof 480 mm width except the chuck portions in the original web of 560 mmwidth was further stretched transversely at the main stretch rate of 6,thereby obtaining a transversely stretched nonwoven fabric with a widthof approximately 2740 mm. Also in this case, the width of thetransversely stretched nonwoven fabric was approximately 2740 mmnarrower than 2880 mm by approximately 140 mm due to shrinkage of thestretched portion. The aforementioned steps-resulted in the transverselystretched web, as a transversely stretched nonwoven fabric, with a totalstretch rate of 9 in a transverse direction in the manufacturingapparatus, a tensile strength of 229.6 mN/tex (2.6 g/d) in thetransverse direction, and a width of 2740 mm (due to the slightshrinkage).

EXAMPLE 3

[0129] In Example 3, an original web with a width of 380 mm obtained bythe spinning apparatus described on the basis of FIG. 2 to FIG. 4 wastransversely stretched using a polyethylene telephthalate molten resinwith a limiting viscosity of 0.56. Unlike the method of performingstretch in two steps as in Examples 1 and 2, this example employedpreheat unit 22 and first transverse stretch unit 23 shown in FIG. 1 totransversely stretch the aforementioned original web of 380 mm width ata stretch rate changed to 9 in the unit, at a stretch temperature of150° C., and a line speed of 45 m/min.

[0130] Since each width of chuck portions on left and right sides of theoriginal web was set at 40 mm in this example as described in Example 1,the distance between the chucks immediately before the stretch was 300mm, and the portion corresponding to the, area of 300 mm width exceptthe chuck portions in the original web before the stretch wastransversely stretched at the stretch rate changed to 9 in the unit. Inthis manner, the portion corresponding to the area of 300 mm widthexcept the chuck portions in the original web of 380 mm width wastransversely stretched at the stretch rate of 9, thereby obtaining atransversely stretched nonwoven fabric with a width of approximately2560 mm. Also in this case, the width of the transversely stretchednonwoven fabric was approximately 2560 mm narrower than 2700 mm byapproximately 140 mm due to shrinkage of the stretched portion in theweb. Such steps resulted in the transversely stretched web, as atransversely stretched nonwoven fabric, with a total stretch rate of 9in the manufacturing apparatus, a tensile strength of 150.1 mN/tex (1.7g/d) in the transverse direction, and a width of 2560 mm (due to theslight shrinkage).

[0131] While preferred embodiments of the present invention have beendescribed using specific terms, such description is for illustrativepurposes only, and it is to be understood that changes and variationsmay be made without departing from the spirit or scope of the followingclaims.

What is claimed is:
 1. A transversely stretched nonwoven fabriccomprising: a plurality of filaments stretched and aligned in atransverse direction and having a fiber diameter of 20 μm or less; saidtransversely stretched nonwoven fabric being stretched in saidtransverse direction at a rate of 7 times or more, and having a tensilestrength of 132.5 mN/tex or higher.
 2. The transversely stretchednonwoven fabric according to claim 1, said nonwoven fabric beingstretched 1.2 to 3 times wider in a transverse direction of an originalweb comprising un-oriented filaments at a temperature higher than itsstretch suitable temperature by 5° C. or more, and then said originalweb stretched 1.2 to 3 times wider in said transverse direction beingstretched in said transverse direction at said stretch suitabletemperature, thereby stretching said original web 7 times wider or morein said transverse direction in total as compared with the state beforethe stretch thereof.
 3. The transversely stretched nonwoven fabricaccording to claim 1, wherein said filaments includes polyethyleneterephthalate as its main component.
 4. The transversely stretchednonwoven fabric according to claim 1, wherein said filaments includespolypropylene as its main component.
 5. A method of manufacturing atransversely stretched nonwoven fabric, comprising the steps of:stretching an original web comprising un-oriented filaments 1.2 to 3times wider in a transverse direction of said original web at atemperature higher than its stretch suitable temperature by 5° C. ormore; and further stretching said original web stretched 1.2 to 3 timeswider in said transverse direction at said stretch suitable temperaturesuch that said original web has a tensile strength of 132.5 mN/tex orhigher in its transverse direction to stretch said original web 7 timeswider or more in said transverse direction in total as compared with thestate before the stretch thereof for manufacturing a transverselystretched nonwoven fabric comprising said filaments of said original webaligned transversely.
 6. The method of manufacturing a transverselystretched nonwoven fabric according to claim 5, further comprising,before the step of stretching said original web 1.2 to 3 times wider insaid transverse direction, the step of: partially bonding said filamentsforming said original web.
 7. The method of manufacturing a transverselystretched nonwoven fabric according to claim 5, wherein an original webcomprising filaments aligned in said transverse direction is used assaid original web before the stretch in said transverse direction. 8.The method of manufacturing a transversely stretched nonwoven fabricaccording to claim 5, further comprising the steps of, in stretchingsaid original web in said transverse direction: disposing a pair of leftand right pulleys with the same peripheral speed symmetrically about acenter line such that the outer peripheries of said paired left andright pulleys have a gradually widening track; circulating a pair ofbelts fitted to belt grooves formed on the peripheral surfaces of saidpaired left and right pulleys on said gradually widening track;introducing said original web at a portion where the space between saidpaired left and right pulleys is narrow; holding one edge portion ofsaid original web in its transverse direction between the belt groove ofone of said paired left and right pulleys and the belt fitted to saidbelt groove, and holding the other edge portion of said original web inits transverse direction between the belt groove of the other pulley andthe belt fitted to said belt groove; and stretching said original webtransversely on said gradually widening track formed by said paired leftand right pulleys.
 9. The method of manufacturing a transverselystretched nonwoven fabric according to claim 5, further comprising thesteps of, in stretching said original web in said transverse direction:using a transverse stretch apparatus of tenter frame of transverselystretching said original web by holding both edge portions of saidoriginal web in its transverse direction in one plane and pulling eachof said both edge portions such that the distance between said both edgeportions is increased.
 10. A method of manufacturing a transverselystretched nonwoven fabric, comprising the steps of: heating an originalweb comprising un-oriented filaments made mainly of polyethyleneterephthalate by hot air at a temperature of 100° C. or higher; andmoving said original web at a line speed of 20 m/min and stretching saidoriginal web 7 times wider or more in its transverse direction such thatsaid original web has a tensile strength of 132.5 mN/tex in thetransverse direction thereof.
 11. The method of manufacturing atransversely stretched nonwoven fabric according to claim 10, furthercomprising, before the step of stretching said original web in saidtransverse direction, the step of: partially bonding said filamentsforming said original web.
 12. The method of manufacturing atransversely stretched nonwoven fabric according to claim 10, wherein anoriginal web comprising filaments aligned in said transverse directionis used as said original web before the stretch in said transversedirection.
 13. A transverse stretch apparatus comprising: first heatingmeans for heating an original web comprising a plurality of un-orientedfilaments to a temperature higher than a stretch suitable temperature ofsaid original web by 5° C. or more; first stretch means for stretchingsaid original web heated by said first heating means 1.2 to 3 timeswider in a transverse direction; second heating means for heating saidoriginal web stretched transversely by said first stretch means to saidstretch suitable temperature; and second stretch means for furtherstretching transversely said original web heated to said stretchsuitable temperature by said second heating means such that saidoriginal web is stretched 7 times wider or more in the transversedirection in total as compared with the state before the stretch of saidoriginal web by said first stretch means.
 14. The transverse stretchapparatus according to claim 13, further comprising first preheat meansfor preheating said original web by blowing hot air toward said originalweb such that said hot air passes through said original web before saidoriginal web is heated by said first heating means.
 15. The transversestretch apparatus according to claim 13, further comprising secondpreheat means for heating said original web by blowing hot air towardsaid original web such that said hot air passes through said originalweb before said original web stretched transversely by said firststretch means is heated by said second heating means to said stretchsuitable temperature.
 16. The transverse stretch apparatus according toclaim 13, wherein each of said first and second stretch means is atransverse stretch apparatus of pulley type including a pair of left andright pulleys with the same peripheral speed and a pair of belts fittedto belt grooves formed on the peripheral surfaces of said paired leftand right stretch pulleys, wherein said pair of left and right pulleysis symmetrically disposed about a center line such that the outerperipheries of said paired left and right pulleys have a graduallywidening track, and said pair of belts fitted to said belt groovesformed on the peripheral surfaces of said pair of left and right stretchpulleys is circulated on said gradually widening track; and saidoriginal web is introduced at a portion where the space between saidpaired left and right pulleys is narrow, and one edge portion of saidoriginal web in its transverse direction is held between the belt grooveof one of said paired left and right pulleys and the belt fitted to saidbelt groove, and the other edge portion of said original web in itstransverse direction is held between the belt groove of the other pulleyand the belt fitted to said belt groove to transversely stretch saidoriginal web on said gradually widening track formed by said paired leftand right pulleys.
 17. The transverse stretch apparatus according toclaim 13, wherein each of said first and second stretch means is atransverse stretch apparatus of tenter frame of transversely stretchingsaid original web by holding both edge portions of said original web inits transverse direction in one plane and pulling each of said both edgeportions such that the distance between said both edge portions isincreased.
 18. A heating apparatus provided for a transverse stretchapparatus for transversely stretching an original web comprising aplurality of un-oriented filaments to manufacture a transverselystretched nonwoven fabric, said heating apparatus comprising: heatingmeans for preheating said original web by blowing hot air toward saidoriginal web such that said hot air passes through said original webbefore said original web is transversely stretched; and a member in netshape for supporting said original web by contacting the surface of saidoriginal web opposite to the side on which said hot air is blown in theportion in which said hot air is blown and passing at least part of saidhot air through said original web.
 19. The heating apparatus accordingto claim 18, wherein said net member is a mesh roll of hollowcylindrical shape rotatably supported and having a plurality of throughholes formed in its wall.
 20. The heating apparatus according to claim18, wherein said net member is a mesh conveyor belt supported movably inone direction.